The present invention pertains to strapping machines. More particularly, the present invention pertains to a modular strap dispenser for a strapping machine, the dispenser having a feed motor to control the feeding of strap directly from the dispenser to the strapping machine, without the need for a strap storage box.
Strapping machines are well known in the art. These machines, also referred to as strappers, are used for positioning, tensioning and sealing a strap around a load. Strapping machines are used for a wide variety of objects from piles of lumber to newspapers and magazines to bales of hay and cotton.
Strapping machines typically include a strapping head and a strap chute mounted to a frame that defines an opening configured to receive a load to be strapped. In most prior art strappers, the strapping head draws a length of strap from a strap supply (typically a coiled spool mounted to a strap dispenser) and feeds the strap around the load through a strap chute. The strapping head then tensions the strap in a tensioned loop around the load, welds the strap in the tensioned state and severs the strap from the supply, thereby forming a tensioned loop about the load.
During the tensioning cycle, a typical strapping head uses motorized feeding mechanism having a pair of feeding rollers to draw the strap forwardly into the strapping machine, through the strap chute and around the load, and a pair of tensioning (or take-up) rollers to draw the strap backwardly past the strapping head and in the direction away from the strapping machine in order to tension the strap.
Since the strapping process inherently involves the repeated, intermittent drawing of strap from the strap supply, and since strap typically is stored in a tightly-wound manner on large, heavy spools having high moments of inertia, the prior art has utilized a strap “storage box” to provide a readily-available amount of “unspooled” strap to the strapping head.
Storage boxes store a length of the strap drawn from the strap supply before the strap is drawn by the strapping head into the strap chute and around the load. In this manner, the unspooled strap in the storage box is available to be used by the strapping head without the inertial resistance associated with drawing the strap directly off of the spool. This results in a more efficient strapping process.
Many prior art storage boxes comprise a box having multiple motorized feeding mechanisms controlled by a sensor. An input feeding mechanism draws strap from the spool and into the storage box. An output feeding mechanism draws strap from the storage box and directs it to the strapping head. The sensor detects the amount of strap in the box and activates the input feeding mechanism when the amount of strap in the box falls below a set level, such as when a length of strap is drawn out of the box by the output feeding mechanism in order to supply strap to the strapping head.
In this manner, a consistent amount of unspooled strap is maintained in the storage box and is available to the strapping head without the need to retrieve the strap directly from the spool. Moreover, the strap stored in the storage box is maintained in a generally non-tensioned state, thereby facilitating the retrieval of the strap by the strapping head over repeated strapping operations.
An additional feature of the storage box is that it provides a place to store “take-up” strap drawn by the strapping head during the tensioning process. During tensioning, such take-up strap is drawn backwardly past the strapping head and in the direction away from the strapping machine in order to tension the strap. The storage box accepts the take-up strap and stores it in preparation for use in the next strapping operation.
While strap storage boxes are an advantageous feature of prior art strapping machines, it would be desirable to eliminate the need for such strap storage boxes in order to simplify the overall design and operation of strapping machines and to reduce cost. Additionally, by decreasing the number of motorized feed mechanisms, the potential for strap misfeeds also would be decreased.
For example, it would be advantageous to use a single feeding mechanism to control the flow of strap from the dispenser, to direct the strap around the strap chute and to tension the strap about the load, rather than using an first input motor to draw the strap from the spool into the strap storage box, a second output motor to draw the strap from the strap storage box to the strapping head and a third motorized feeding mechanism at the strapping head to direct the strap around the strap chute and to tension the strap about the load.
Accordingly, there exists a need for a strap dispenser having a feed motor for use with a strapping machine. Desirably, the dispenser eliminates the need for a strap storage box by providing strap to the strapping machine on demand. More desirably, the dispenser includes an accumulator box for storing take-up strap. More desirably still, the dispenser has a single feed motor configured to draw the strap directly from the coiled spool, feed the strap to the strapping machine, feed the strap around the strap chute of the strapping machine and tension the strap about the load. More desirably yet, the dispenser includes a controller configured to control the speed and direction of the feed motor. Most desirably, the strap dispenser is modular and may work in conjunction with several different types of strapping machines.